docs: def _get_regional_term(self, C, imt, vs30, rrup):
          """
          In accordance with Abrahamson et al. (2014) we assume as the default
          region California
          """
          vs30star = self._get_vs30star(vs30, imt)
          return C['a31'] * np.log(vs30star/C['vlin']) + C['a25'] * rrup